Abstract: An interface device for thermally coupling an integrated circuit to a heat sink having a first material characterized by high thermal conductivity such as copper, where the copper completely surrounds a plurality of inner core regions. The plurality of inner core regions contain a low coefficient of thermal expansion material and are primarily disposed in the copper material in the region directly under the integrated circuit. The low expansion regions retard thermal expansion of the interface device during exposure to variations in the temperature, yet there are continuous paths of copper provided between the integrated circuit and heat sink to promote efficient heat transfer between the silicon chip to the heat sink through the high conductivity copper. In addition, high thermal resistance layers are provided for dielectric isolation between an integrated circuit chip and heat sink, when necessary, using this invention.